Key factors for the design of synchronous reluctance machines with concentrated windings

This paper presents the key factors to designing a synchronous reluctance machine with concentrated windings. For synchronous machines the stator and pole configuration is commonly chosen according to the highest winding factor and lowest air-gap leakage factor. However, this does not always lead to the best machine. Due to the discrete field distribution of concentrated tooth windings, the air-gap harmonic content increases. This results in a high leakage inductance and a high leakage factor and consequently in a low saliency ratio of the machine. In addition to the theory of winding- and air-gap leakage factors for synchronous machines this paper introduces an analytic torque factor which is valid for all stator and rotor configurations. The torque factor describes the rotor pole utilization depending on the winding configuration. The presented discussion is based on analytic equations and finite element simulations of two segmented synchronous reluctance machines.